1. Field of the Invention
This invention generally relates to a drive train system for utility vehicles. A positive pressure approach is used in maintaining air flow through a drive train enclosure. Special application is found for this approach in continuously variable transmissions suitable for use on utility vehicles. The positive pressure achieved by this invention prevents dust and water from entering the transmission enclosure at virtually all times during operation of the vehicle. More particularly, the invention relates to a positive air flow system that operates independently of transmission rotation or operation.
2. Description of Related Art
Utility vehicles of the type which are suitable for all-terrain usage and the like are provided. Utility vehicles are generally four-wheeled vehicles, which are oftentimes operated in harsh conditions with deep water, thick mud, or the like and the problem of maintaining the drive system in working order has been addressed in the past. Examples include utility vehicles illustrated in Mizuta U.S. Pat. Nos. 5,086,858, 6,394,555, 6,460,916, 6,517,111, 6,523,879 and 6,616,207, each being incorporated by reference hereinto. The '858 Mizuta patent particularly shows an air intake system for a utility vehicle. A belt converter drive system is shown with a cooling assembly. The cooling assembly has an air intake which is located on the upper part of the frame of the vehicle. Cooling fan blades revolve with the engine for cooling the belt converter in that arrangement.
Lislegard U.S. Pat. No. 6,176,796, incorporated by reference hereinto, shows a continuously variable transmission with a clutch having enhanced air cooling. This relates to cooling of a continuously variable transmission (known as a CVT). By this patent, air cooling channels are located in the outer surface of one or more of the sheaves on the clutches. The structure and operation of CVT units are found, for example, in U.S. Pat. No. 3,861,229, incorporated by reference hereinto. In the '796 patent, the fins are radially oriented and extend axially from the outer face of the sheave body. In operation, air flow is generated by the fins only when the fins are in rotation when the sheave on which they are positioned is in rotation. Thus, operation of the fins is not independent of operation of the CVT. Air flow is imparted only when the CVT is in operation, but that has been found to be insufficient because the CVT is subject to intrusion by dirt, rainwater, and the like even when the vehicle is in idle mode.
Heretofore, fins and fan arrangements associated with drive trains of utility vehicles have been provided in an effort to cool drive train components. The present invention improves substantially upon this general approach by providing a CVT assembly which has an enclosure having a positive air flow pressure which is not directly driven by a drive train component and which preferably flows longitudinally through the enclosure. An independently-powered cooling/pressurization module for a traction drive housing was proposed in U.S. Pat. No. 4,878,467 (Schmidt). This proposed design is problematic. For example, the blower fan which is proposed introduces coolant into the housing at a direction perpendicular to the rotational plane of the drive components. As a result, the coolant flow path is relatively constrained, so pressurization and cooling are diminished at areas offset from the coolant inlet. Furthermore, adequate cooling of the drive components is not assured, and the pressure along the seams of the housing can be insufficient to reliably prevent the intrusion of moisture and outside particulates.
Accordingly, a general object and aspect of the present invention is to provide an improved drive train unit for a utility vehicle.
Another object or aspect of this invention is to provide an improved drive train unit with an integral module which simultaneously performs a cooling and cleaning function.
Another object or aspect of this invention is to provide an improved drive train unit that uses positive air flow into a CVT enclosure in order to effectively address risks of having dirt, dust or moisture enter the enclosure and potentially foul the CVT and its operation.
Another object or aspect of the present invention is to provide a means for pressurizing a CVT enclosure or housing even while the utility vehicle is in its idle mode.
Other aspects, objects and advantages of the present invention, including the various features used in various combinations, will be understood from the following description according to preferred embodiments of the present invention, taken in conjunction with the drawings in which certain specific features are shown.